Modeling the impact of future rainfall changes on the effectiveness of urban stormwater control measures.

The convergence of urban expansion, deteriorating infrastructure, and a changing climate will escalate the risks of stormwater pollution and urban flooding in the coming decades. Using outputs from an ensemble of global climate models to drive a high spatial resolution stormwater model, we analyzed climate change impacts on urban stormwater runoff and control measures for 23 cities across the United States. Runoff model outputs for two future emissions scenarios ending in 2055 were compared against a historical scenario to assess changes. All cities showed increases in average annual stormwater runoff, with changes up to 30% over the next 30 years due to a greater frequency of high intensity storm events. Runoff model outputs showed substantial variation across cities with untreated stormwater runoff increasing by as much as 48%. Patterns of future runoff impacts within cities will affect the performance of distributed treatment strategies such as Green Stormwater Infrastructure (GSI) to meet municipal water quality improvement and runoff reduction goals. Results indicate that adoption of adaptable design standards and decision support tools that readily accommodate projected precipitation changes are critical for supporting more resilient designs of stormwater control measures.

Quantifying clogging patterns of infiltration systems to improve urban stormwater pollution reduction estimates.

Infiltration systems are among the most commonly implemented practices to control urban stormwater and to attenuate pollutant delivery to receiving waters, because they are relatively cheap to build and amenable to space constraints in urbanized areas. However, infiltration systems tend to clog with sediments, which can rapidly reduce their performance. While clogging has been consistently identified as a significant determinant on infiltration BMP (best management practice) performance and lifespan, there have been few methods reported to predict rates of clogging or incorporate insights to urban catchment water quality modeling. We ran a series of laboratory and field experiments to identify clogging mechanisms and quantify infiltration performance declines as a function of sediment loading. The results show rapid initial declines of infiltration rate, primarily due to accumulation of material at the bottom of the infiltration BMP. The performance decline trajectories were sensitive to BMP geometry, with BMPs that had greater lateral infiltration surface area declining less quickly. We integrated these experimental results to a spatially distributed stormwater model to illustrate how they can be used to predict BMP performance declines over time and assess cost trade-offs. Results will be used to adapt algorithms in a cloud-based stormwater management platform to better inform maintenance needs for cities and improve the accuracy of urban stormwater pollutant load reduction estimates that support regulatory compliance tracking.